Reflective Glass shader, like those in our window
The standard Glass shader gives you exactly that.
Or if you prefer Principled BSDF like me:


Set Transmission to 1
Use Roughness and Transmission roughness to control the glass type
Add thickness to your glass for realistic results


Suzanne on one side, and a black material on the other to make a mirror



To make this work in Eevee


enable Refraction in the Render tab
enable Screen Space Refraction in your material settings